Alloys, such as high rhenium containing alloys, used for casting single crystal, directionally solidified parts can be very expensive. In conventional art casting systems, molten alloy is introduced to the mold by pouring or injecting the alloy from the top into a sprue passage. To minimize defects in cast parts caused by shrinkage during solidification, directional solidification can be employed wherein the shrinkage that forms in solidified portions of the part are filled with alloy from a portion of the part that has not yet solidified and with molten alloy in the sprue replenishing any material used to fill the shrinkage. In these conventional casting systems, alloy solidifies in the sprue and must be removed from the finished parts and scrapped or recycled.
For high cost alloys it is advantageous to minimize or reduce the material remaining in the sprue following the casting process. A counter-gravity process that addresses this need was first developed by Hitchiner Manufacturing Company and disclosed in U.S. Pat. No. 3,863,706, the disclosure of which is incorporated in its entirety by reference herein. In the counter-gravity process disclosed in that patent, the sprue is filled from the bottom and, following solidification of the cast parts, any molten metal in the sprue is allowed to drain down and be recaptured for subsequent casting processes thereby reducing the overall cost per cast part. Further reductions in cost per part can be achieved by reducing cycle time for casting.
While counter-gravity mold filling processes and methods are an improvement over conventional casting methods and apparatus, the equipment for performing these processes has heretofore been oriented vertically and can extend upwards of 40 feet or more. Because of this, these processes can only be performed in suitable locations having extended vertical space or in locations in which a pit has been created for containing a portion of the equipment.
Improvements are therefore still needed to improve efficiency, reduce cost, allow use of the processes in a broader selection of locations and to allow use of these methods and apparatus to be used in single crystal casting.